The crystalline morphology of poly(vinylidene fluoride)/poly(methylmethacrylate) blends

Abstract Poly(vinylidene fluoride), PVF 2 , as well as blends of PVF 2 with poly(methyl methacrylate), PMMA, develop a variety of crystalline morphologies at low undercoolings. Both the α and γ crystal forms grow from the melt and the former undergoes a solid‐solid phase transition to the latter, though its morphology remains unaltered. Three melting temperatures which decrease with increasing PMMA content are observed. Hoffman‐Weeks analysis shows the equilibrium melting points of the blends to be depressed. Using these equilibrium values, the thermodynamic interaction energy density is calculated to go from −5.40 × 10 6 to −2.96 × 10 7 j/m 3 as the blend composition goes from 40.1 volume percent to pure PVF 2 . The band periodicity in the α form spherulites increases with crystallization temperature and PMMA content and it appears to be from a lamellar reorientation process with an apparent activation energy of 322 cal/mole. Electron diffraction patterns taken along the radial direction in a given spherulite reveal lamellar twisting which causes the banded appearance. Light scattering results suggest that the lamellar are formed into rod‐like structures on a local scale but that on a larger scale they develop a disoriented spherulitic morphology.